Motorcycle parts outgoing / incoming customs

[TT2]

I've brought loads of parts and riding gear into Thailand over the years. Last time my bags got scanned by Thai customs and I had two bags full of parts and riding gear (mostly used, some new). I didn't get fined or anything but they told me not to do it again. I didn't even know it was a big deal until then.

 

I plan on taking a pair of motorcycle wheels with me out of Thailand, having them powdercoated, then bringing them back into Thailand. It's a short duration trip, I've got loads of unused baggage capacity, and my friend will do the work for free. What forms, etc. do I need to complete / submit when leaving Thailand so I am able to bring the wheels back and not have problems?

[VocalNeal]

Except for the free. Why not simply get them powder coated here? Not ridiculously expensive. Might be less hassle.